U.S. patent number 4,089,744 [Application Number 05/738,604] was granted by the patent office on 1978-05-16 for thermal energy storage by means of reversible heat pumping.
This patent grant is currently assigned to Exxon Research & Engineering Co.. Invention is credited to Robert P. Cahn.
United States Patent |
4,089,744 |
Cahn |
May 16, 1978 |
Thermal energy storage by means of reversible heat pumping
Abstract
A method is described for storing the offpeak electrical output
of an electricity generating plant in the form of heat by using it
to raise the temperature level of a quantity of stored heat
retention material and recalling said stored heat during periods of
peak power demand in the form of electrical power. During low power
demand periods hot water is drawn from a hot water storage means
and cooled by flashing it at successively lower pressures. The cold
condensate is sent to a cold water storage means while the various
flash vapors are fed to appropriate stages of a steam compressor
driven by excess power drawn from the electricity generating
station. The steam which has been compressed by means of the excess
electrical power is directed to heat exchanger means where it is
used to heat a low vapor pressure (LVP) thermal energy retention
material flowing from cold to hot storage means through the heat
exchanger means. By the practice of this invention, heat is
transferred, by means of the steam compressor powered by excess
electrical power, from hot water (.about. 210.degree. F) to the LVP
material raising its temperature from a cold storage temperature of
about 190.degree.-300.degree. F to a hot storage temperature of
about 450.degree.-600.degree. F. The hot LVP material is stored at
atmospheric pressure preferably under an inert gas atmosphere.
During peak energy demand periods, the process is reversed and the
hot LVP material is used to generate steam which runs a turbine
thereby producing electrical power from a generator.
Inventors: |
Cahn; Robert P. (Millburn,
NJ) |
Assignee: |
Exxon Research & Engineering
Co. (Linden, NJ)
|
Family
ID: |
24968697 |
Appl.
No.: |
05/738,604 |
Filed: |
November 3, 1976 |
Current U.S.
Class: |
376/322; 376/402;
60/648; 60/652; 60/659; 60/676 |
Current CPC
Class: |
F01K
3/00 (20130101); F01K 3/006 (20130101) |
Current International
Class: |
F01K
3/00 (20060101); G21C 015/12 () |
Field of
Search: |
;176/39,87
;60/644,648,652,659,676 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Nelson; Peter A.
Attorney, Agent or Firm: Allocca; Joseph J.
Claims
What is claimed is:
1. A process for storing the excess electrical output of an
electricity generating system by raising the temperature level of a
quantity of stored low vapor pressure (LVP) organic heat retention
material, and recalling said heat from said LVP organic heat
retention material during periods of peak power demand for
reconversion into electrical power comprising the steps of:
(a) during periods of low power demand drawing hot water from a hot
water storage location means;
(b) flashing said hot water at successively lower pressures to
generate steam and cooling resultant residual water condensate to
form cold water which is stored in cold water storage location
means;
(c) conducting said flashed steam to various stages of a
compression means;
(d) driving said compression means by means of a motor means
powered by means of excess electrical power produced by an
electricity generating system;
(e) compressing the flashed steam in the compression means being
driven by the excess electrical power;
(f) conducting the compressed steam at different pressures from the
different stages of the compression means to heat exchanger
means;
(g) contacting the compressed steam with a low vapor pressure
organic thermal energy retention material moving from a cold
storage location means to a hot storage location means through the
heat exchanger means of (f);
(h) storing the hot LVP thermal energy retention material in the
hot LVP material storage location means;
(i) during periods of peak power demand converting water into steam
by contacting said water with hot LVP material moving from hot
storage location means to cold storage location means, said
contacting occurring in heat exchanger means;
(j) conducting the steam generated in step (i) from the heat
exchanger means to an expansion engine means thereby converting
heat energy into mechanical motion;
(k) running a generator by means of the mechanical motion produced
in step (j) thereby effecting the conversion of heat back into
electricity;
(l) condensing the spent steam by means of cold water being passed
from said cold water storage location means to said hot water
storage location means; and
(m) storing the hot water produced in step (1) in said hot water
storage location means for use during lower power demand system
charging periods as the hot water of step (a) above.
2. The process of claim 1 wherein the hot low vapor pressure
organic heat retention material stored in step (h) is at a
temperature of from 450.degree. to 600.degree. F and the cold LVP
material stored in step (i) in the cold storage location means is
at a temperature of about 150.degree.-300.degree. F.
3. The process of claim 1 wherein the low vapor pressure organic
heat retention material is a hydrocarbon distillate boiling between
500.degree.-1300.degree. F.
4. The process of claim 3 wherein the hydrocarbon distillate is
selected from the group consisting of a 650.degree.-1050.degree. F
vacuum gas oil cut, a 600.degree.-950.degree. F catalytically
cracked cycle stock, a 600.degree.-1000.degree. F thermally cracked
gas oil cut, a 600.degree.-1000.degree. F doubly extracted and
dewaxed vacuum pipe still cut, a 600.degree.-900.degree. F VT
hydrocracked cut and a 600.degree.-900.degree. F VT coker gas oil
wherein all of the above materials have been hydrotreated.
5. The process of claim 3 wherein the low vapor pressure organic
heat retention material contains 1% or less anti-oxidants and
dispersants.
6. The process of claim 5 wherein the antioxidants are selected
from the group consisting of hindered phenols.
7. The process of claim 5 wherein the dispersants are selected from
the group consisting of sulfonates.
8. A process for storing the excess electrical output of an
electricity generating plant by conversion into heat and recalling
said heat during periods of peak power demand by reconversion into
electrical power comprising the steps of:
(a) during periods of low power demand drawing hot water from a hot
water storage location means;
(b) conducting said hot water to heat exchanger means;
(c) contacting said hot water in heat exchanger relationship with a
heat transfer fluid;
(d) vaporizing said heat transfer fluid and directing the resultant
cool water via a cooler into a cold water storage location means;
`(e) conducting the heat transfer fluid vapor of step (d) to a
compression means;
(f) compressing said heat transfer fluid vapor in the compressor
means by utilizing excess electrical power of a power source;
(g) contacting and condensing said compressed heat transfer fluid
vapor in heat exchanger relationship with a low vapor pressure
(LVP) organic thermal energy heat retention material moving from
cold storage location means to hot storage location means through
the heat exchanger means;
(h) storing the hot LVP material;
(i) during periods of peak power demand using hot LVP material
moving from hot storage location means to cold storage location
means to vaporize a heat transfer fluid in heat exchanger
means;
(j) directing said hot heat transfer fluid vapor to an expansion
engine;
(k) running the expansion engine on the heat transfer fluid vapor
thereby converting thermal energy into mechanical energy;
(l) using the mechanical energy produced by the expansion engine to
run a generator thereby yielding electrical power;
(m) condensing the expanded heat transfer fluid vapor by means of
cold water flowing from cold water storage location means to hot
water storage location means; and
(n) storing said hot water in a hot storage location means for use
in step (a) during system charging periods.
9. The process of claim 8 wherein the heat transfer fluid is
selected from the group consisting of freon, water, propane,
propylene, butanes, ammonia and pentanes.
Description
DESCRIPTION OF THE INVENTION
A method is described for storing the off peak electrical output of
an electricity generating plant by raising the temperature level of
a quantity of stored heat retention material and for recalling said
stored heat during periods of peak power demand in the form of
electrical power. The process utilizes hot low vapor pressure (LVP)
thermal energy retention material and appropriate storage means and
cold LVP thermal energy retention material and appropriate storage
means, a hot water storage means and a cold water storage means,
heat exchanger means, steam compressing means, steam turbines,
electric motors and electricity generating means. In a preferred
embodiment, the steam compressing means and steam turbines may be a
single dual purpose apparatus. The same is true for the electric
motors and electricity generating means. During periods of low
power demand hot water is withdrawn from its storage means and
cooled by flashing it at successively lower pressures. The various
flash vapors are fed to the appropriate stages of steam compressing
means driven by excess power drawn from an electricity generating
system. Cold water from the last flash stage and by way of cascade
from all previous flash stages, is cooled and stored in cold water
storage means. The steam which has been compressed in the steam
compression means by means of the excess electrical power flows at
different pressures from the steam compression means to heat
exchanger means where it is used to heat LVP thermal energy heat
retention material flowing from cold storage means to hot storage
means through the heat exchanger means. By the practice of the
instant invention heat has been transferred, by means of the steam
compression means powered by excess electrical power, from the
water (at about 100.degree. to 210.degree. F) to the LVP material,
raising the temperature of the LVP material from about
150.degree.-300.degree. F (cold) to about 450.degree.-600.degree. F
(hot). In effect, the excess electrical power has been used to
raise the temperature level of stored heat.
During periods of peak power demand the above-recited process is
reversed, the hot LVP material being used to generate steam which
in turn powers a turbine thereby running an electrical power
generating means to produce electricity, i.e. the conversion of the
stored heat at a high temperature level back into electricity and
stored heat at a lower temperature level.
By the practice of this invention the excess power generated during
off-peak periods can be stored for recall during high power demand
periods without the use of gas turbines, etc., which consume our
limited and costly natural resources (and increases air and water
pollution levels) or the necessity of designing and building overly
large power stations merely to handle relatively short term high
power demands. The process of the instant invention is independent
of the type of electric power station involved, it being useful
with nuclear, fossil fuel, solar, geothermal, hydroelectric, tidal,
hydrothermal, etc. Since it is the excess electric power which is
being stored by conversion into heat, the energy storage,
reconversion and utilization means disclosed in the instant
invention can be sited close to the load demand area, i.e. close to
the center of a metropolitan area since the energy used to charge
the heat storage means is excess electric power (traveling over
conventional power lines). The storage and retrieval system does
not have to be sited near the power plant. Pollution problems are
avoided since no fuels are expended in practicing this invention.
The power stations which produce the excess electrical power
benefit tremendously from the instant invention since they can be
run at maximum efficiency. In the case of nuclear power plants, the
reactors need not be throttled (a difficult and inefficient use of
such a plant). In the case of modern fossil fuel plants, the
pollution control devices can be designed and sized for maximum
efficiency since the plant can be run at a steady state. Power
stations which run in cyclic fashions due to fluctuating power
sources (i.e. solar) can be designed for maximum output, with the
excess output being stored so as to level the load enabling a
cyclic or unavoidably variable output station to satisfy load
demand which do not match the output characteristics of the
station.
In addition, it can be retrofitted into any power system subsequent
to the design and construction of any of the power plants in the
system.
PRIOR ART
French Pat. No. 2,098,833 issued Mar. 10, 1972 to
Babcock-Atlantique discloses a heat accumulation system for
balancing off-peak and peak demands in a thermal power producing
unit. The heat accumulation system stores the high level heat made
available at the power house by means of a compressor which acts as
a heat pump on high pressure primary steam during off-peak periods.
This enables the temperature of a heat transfer fluid to be raised
to a temperature sufficient to superheat steam to a high pressure
turbine during peak demand periods so that a power unit with a
rated capacity below peak load can carry the load by utilizing this
heat stored during off-peak periods. The process utilizes as a heat
source, the primary high pressure steam drawn from the power cycle,
an expansion machine for the working fluid, means for circulating
one or more fluids, a heat accumulator and an apparatus for
compressing the fluid containing the heat to be stored before
transferring the heat to the accumulator. The heat accumulator used
in the system is a single vessel wherein the heat is stored by its
transfer from a heat transfer fluid to corrugated plates. The heat
is stored in the ceramic packing of the accumulator which of
necessity results in a continuous degrading of the level of the
heat on the accumulator. The important difference is that patentee
is sited at the powerhouse and works with the primary power cycle.
The instant invention is independent of location, cycle, retrofit
size of unit and flexibility and nuclear regulations, safety, oil
contamination and oil fouling of the main plant heat
exchangers.
By way of comparison, the instant invention utilizes stored hot
water as a primary heat source for the charging cycle and a stored
mobile heat retention material, that is, a heat retention material
moving from a hot storage location to a cold storage location. Such
movement of the LVP thermal energy heat retention material exhibits
the distinct advantage over nonmoving heat retention systems
(accumulators) in that by moving the LVP material the water being
heated and boiled is continuously being contacted with full high
temperature LVP material for as long as there is material stored in
the high temperature vessel. This means that for the entire period
of peak power demand, or for as long as there is material stored in
the hot storage vessel the water will contact uniformly hot
material and will therefore be converted to steam under constant
conditions. By comparison, in a fixed bed thermal accumulator heat
is stored by passage of a hot thermal energy carrier fluid through
the bed. On flowing from one end to the other of said accumulator,
the fluid will give up heat by thermal conduction to the solid
tiles or ceramic particles making up the bed, resulting in a
temperature front advancing along the bed in the direction of flow.
Behind this front, the temperature of the solid will be close to
the temperature of the entering hot fluid. Ahead of this front the
temperature of the solid and fluid will be essentially that of the
packing when the operation started. The width of the front (length
of bed over which the temperature changes from that of the hot
fluid to that of the cold packing) is a function of many parameters
including heat capacities and heat transfer properties, fluid flow
rate, bed and particle diameter, etc. Also, the regularity or
evenness of the front is very much a function of flow distribution,
channeling, flow rates, etc.
The same holds true when the bed is hot and the entering fluid is
cold, except all temperature indications are reversed.
The net effect of using a fixed bed accumulation at initial
temperature T.sub.a on a fluid flowing through it with initial
temperature T.sub.i is that the fluid will leave the accumulator at
a temperature close to T.sub.a for a period of time set by the time
required for the above temperature front to advance through the
length of the accumulation. This time is strictly a function of the
heat capacity of the flowing fluid vs the heat capacity of the
total accumulator packing.
When the front of the temperature front "break-through" reaches the
end of the accumulator, the temperature of the fluid leaving the
accumulator will slowly change from close to T.sub.a to close to
T.sub.i. The ratio of the length of time over which the effluent
fluid is at a more or less constant temperature T.sub.a to the
length of the varying temperature period is a measure of the
efficiency of the solid accumulator method of storing heat. In real
world situations due to slow heat transfer, poor liquid
distributions and channeling and superimposed thermal convection
currents, the ratio of constant/varying effluent temperature
periods is not sufficiently high to make this a preferred method of
storing heat. Other disadvantages of storing heat in a solid
accumulator system are expansion and contraction of the solid
resulting in stresses and breakage, formation of fines which foul
exchanger and the high cost of the accumulator and filtering
devices. The specific heat of solids is usually much lower than
that of liquids, resulting in a large weight and physical volume
(allowing for voids) penalty and corresponding interstitially held
up liquid in these large packed containers.
Another difference is that the invention of Babcock-Atlantique has
its compression step work upon high pressure primary steam drawn
from the boiler. This primary steam is sent to a compressor powered
by direct coupling to the turbine. Of necessity this system must be
located within the very confines of the power station. By
comparison, the process of the instant invention utilizes stored
hot water as to charging cycle heat source, flashes this hot water
to steam which nonprimary steam is then compressed in heat pump
means, said heat pump being run by excess electrical power drawn
from the power grid.
In the practice of this invention, the heat storage medium is
described as a low vapor pressure organic heat retention material.
Such an LVP material is a hydrocarbon oil preferably one derived
from petroleum by distillation and refined, if necessary, by
catalytic treatment for the hydrogenation of unsaturates and/or for
the removal of sulfur and/or nitrogen in the presence of hydrogen
under pressure utilizing any of the standard catalysts known in the
art such as cobalt-molybdenum, nickel-molybdenum, etc. The
hydrocarbon distillate can also be treated by means of solvent
extraction to remove unstable, easily oxidized compounds which
could lead to sludge and deposit formations on hot heat exchanger
means surfaces. The LVP material can also be dewaxed by use of
appropriate low-temperature crystallization/separation techniques
known in the art to improve the low temperature handleability,
(i.e. viscosity and fluidity) of the material. Before being treated
as described above, the hydrocarbon distillate can be thermally
and/or catalytically cracked to remove any thermally unstable
material present but such cracking should be followed by
hydrogenation to remove any unsaturates resulting from the
cracking.
The hydrocarbon distillate used should be the fraction within the
boiling range of 500.degree. to 1300.degree. F, preferably
600.degree. to 1100.degree. F and most preferably 650.degree. to
1000.degree. F. The vapor pressure of the material used for such
thermal energy storage should not exceed 1 atmosphere at the
maximum utilized storage temperature and should preferably be below
0.25 atm and most preferably below 0.1 atm. Such low vapor
pressures are preferred since they facilitate the use of
unpressurized storage means, transport means and heat exchanger
means and such unpressurized systems are naturally more economical,
desirable and more easily maintained. Such materials of low vapor
pressure are kept in isolation from the environmental atmosphere so
as to avoid material degradation, by means of an inert gas
atmosphere blanketing the stored material or may be accomplished by
use of an insulated floating roof or diaphragm type apparatus over
the stored material, or by a combination of these two systems. It
should be noted that the higher the vapor pressure, or even the
closer the vapor pressure gets to 1 atm problems arise in systems
isolation and materials handling. Inert gas transfer and balance
between hot and cold storage means is a potential problem when the
organic material has a vapor pressure approaching or exceeding 1
atm at the hot storage temperature.
Typical materials which qualify as LVP organic heat retention
materials are exemplified but cannot be viewed as exhaustively
disclosed by the following:
Vacuum gas oil obtained from crude 650.degree. F VT atmosphere
pipestill bottoms by running in a vacuum pipestill, getting a
650.degree./1050.degree. F VT cut. followed by hydrodesulfurization
over a catalyst in the presence of H.sub.2 under pressure;
The vacuum gas oil described above further treated by solvent
extraction to remove unsaturates, sulfur and nitrogen compounds and
aromatics;
Catalytic cracking cycle stock with a boiling range of from about
600.degree. to 950.degree. F drawn from a recycle catalytic cracker
followed by hydrotreating. The feed to the catalytic cracker, which
is usually a material with a boiling range of from 500.degree. to
900.degree. F may but does not necessarily have to have been
hydrotreated for sulfur removal prior to cracking;
Thermally cracked gas oil, i.e. steam cracked gas oil in the
600.degree. to 1000.degree. F boiling range after appropriate
catalytic hydrotreating to saturate olefins and diolefins and to
decrease sulfur and nitrogen content;
Double extracted and dewaxed 600.degree. to 1000.degree. F VT
vacuum pipestill fraction, suitably hydrotreated (hydrofined);
600.degree. to 900.degree. F VT fraction obtained from
hydrocracking, a process in which heavy gas oils are catalytically
broken down and hydrogenated over a catalyst in one or more
steps;
600.degree. to 900.degree. F VT coker gas oil suitably stabilized
by catalytic hydrogenation.
The sulfur levels in the feeds considered may range, prior to
hydrogen treatment, from 0.3 to 5.0% and should be of the order of
0.05 to 1.0% following treatment.
Oxidation stability additives and sludge dispersants and
depressants may be added to the material to improve its performance
in the hot LVP thermal energy retention material (i.e. oil) storage
locations. Typical antioxidants are hindered phenols, such as
t-butyl phenol and typical dispersants may be sulfonates or ashless
dispersant based adducts. The content of the antioxidants and
dispersants in the LVP material will preferably be below 1%
each.
BRIEF DESCRIPTION OF THE DIAGRAMS
Diagram I is a schematic representation of the basic heat
storage-retrieval system utilizing reversible heat pumping.
Diagram II represents a modification of the basic concept using
independent intermediate loops in conjunction with an intermediate
heat transfer fluid .
Diagram I is a schematic representation of the basic concept of the
instant invention. Arrows appearing directly on the conduit lines
indicate direction of material flow during discharge operation
while arrows appearing adjacent to conduit lines indicate direction
of material flow during charging operations.
At the start of the charging operation which normally occurs during
low power damand periods, i.e. during periods when excess
electrical power is available the hot water vessel 1 is full, cold
water vessel 2 is empty, cold low vapor pressure material (oil for
the sake of brevity) storage vessel 3 is full and hot oil storage
vessel 4 is empty.
The stored hot water from (1) is directed successively through
conduits 5-5C to reversible pumps 6.fwdarw.6C (these pumps are
optional) and from 6-6C to conduits 7-7C for introduction into
flash drums/condensers (8-8C) wherein the hot water is successively
flashed at successively lower pressures to yield steam at
decreasing pressure and residual water at decreasing temperature.
This water is combined with the hot water moving in cascade fashion
from condensers 13 to 13C. At the last flash drum/condenser the
water which remains and which cannot be flashed to steam is
directed through conduit 20 to conduit 21 for passing through
coolers, which may be air coolers 22 and then through conduits 24
through reversible pump 23 to storage in cold water storage means
(2). The steam from the different flash drums 7-7C is fed by
conduits 9-9C to the compressor/turbine 10 at varying stages.
Compressor/turbine 10 is driven by excess power drawn from the
power grid which excess power is used to run the motor/generator 11
which in turn drives the compressor/turbine. Steam compressed at
different pressures within the compressor/turbine 10 by means of
excess grid power is directed through conduits 12-12C to heat
exchanger means 13-13C wherein the high temperature steam from the
compressor/turbine 10 is contacted by direct or indirect heat
exchanger with cold oil drawn from storage means 3 and directed
through conduit 14 to heat exchangers 13-13C. At the heat
exchangers the cold oil is heated by contacting with the high
temperature compressed steam. This heating is conducted so that the
oil is being heated with steam of continuously higher condensing
temperature. The condensate from each successive heat exchanger is
directed cascade fashion to successively lower temperature
exchanges through conduits 15-15B and optional reversible pumps
16-16B. In this manner, maximum heating efficiency is achieved. The
hot oil in conduit 14 after passage through the last heat exchanger
is directed to storage means 4. The condensate from the last heat
exchanger is directed through conduit 17 and reversible pump 18 to
hot water storage means 1 or to flash drum 8.
During periods of peak power demand all flows are reversed, the hot
oil being used to heat water in the heat exchanger to produce steam
of varying pressure which steam is fed to a turbine to generate
electrical power. The spent steam is led to condensers where it is
converted to hot water, at the same time heating cold water being
pumped from cold water tank to hot water tank 1 through condensers
8C to 8. Hot water is stored for use during low power demand
periods.
This system has the major advantage of being completely independent
of the location of the power station since the excess power which
is stored is electrical power coming off the grid which power is
converted indirectly to heat by running a compressor. By this means
the storage facility can be located a considerable distance from
the power station; the storage facility can be sited at the very
heart of the peak demand load center. Furthermore, the facility is
completely independent of the source of the power. The power can be
generated by hydroelectric, nuclear, solar, fossil fuel, tidal,
geothermal, fusion, etc., stations. As long as the power is in the
form of electricity it can be stored by utilization of this
process.
The heat pump energy storage-energy retrieval system can also be
located close to the electricity source. When this is done, the LVP
thermal energy heat retention material is heated by means of
turbine extraction steam and primary high pressure steam as
described in Ser. No. 533,263, now U.S. Pat. No. 3,998,695 and Ser.
No. 613,754, now U.S. Pat. No. 4,003,786. The stored hot LVP
thermal energy retention material can be used either to preheat
boiler feed water (as taught in U.S. Pat. No. 3,998,695 and
4,003,786) or it can be used to generate steam to run a turbine (as
taught as the second step of the instant process), or both
processes can be practiced simultaneously. It should be noted that
when the heat pump facility is located close to an electricity
source, the equipment of the heat pump facility is available as an
auxiliary electricity generating station. In the event the
neighboring primary electricity source is forced to shut down, the
heat pump facility can then function as described in the instant
specification, drawing electric power from the main power grid
converting it to heat, storing said heat and reconverting the
stored heat into electricity during periods of peak power
demand.
In an alternative embodiment an independent intermediate loop can
be employed between the stored, moving hot water-cold water circuit
and the stored moving hot LVP material-cold LVP material circuit.
Referring to Diag. II, during charging, the stored hot water is
contacted in heat exchanger means with an independent intermediate
heat transfer fluid such as freon, ammonia, propane, propylene,
butane, pentane, water, i.e. any thermal fluid which has
characteristics compatible with compression means-expansion means
operations. This thermal fluid in the independent circuit is
vaporized by its contact with the hot water and is compressed in
the compression means which is run by a motor powered by excess
electricity drawn from the power grid. This compressed vapor, now
at a higher temperature, is contacted in heat exchanger means with
an LVP organic thermal energy retention material moving through
said exchanger means on its passage from cold to hot storage means.
During periods of peak power demand the hot LVP material is
transported to cold storage means through heat exchanger means
wherein the hot LVP material is contacted, directly or indirectly,
in heat exchanger means with the intermediate heat transfer fluid
previously described moving through the independent intermediate
loop thereby transferring heat to said fluid and evaporating it at
elevated pressure. Said fluid thereupon is conducted to a heat
engine whereby its thermal energy is converted to mechanical energy
which is used to power a generator resulting in the production of
electricity. The intermediate heat transfer fluid transfers its
residual heat (usually in the form of latent heat) to water in heat
exchanger means whereby said water is heated and stored for use
during nonpeak periods as disclosed above.
During periods of low power demand, valves III and I are closed,
permitting the passage of the intermediate heat transfer fluid in
the independent loop through the heat pump thereby raising its
temperature prior to contacting with the LVP thermal energy
retention material resulting in heat transfer. During periods of
maximum power demand, valves IV and II are closed (III and I open)
directing the flow of the intermediate heat transfer fluid heated
by the moving hot LVP material through the heat engine thereby
generating current. The partially spent intermediate heat transfer
fluid coming from the heat engine is used to heat cold water which
is then stored as hot water for use during periods of low power
demand as a heat source. Conduits A and B may be combined into a
single conduit by the application of ordinary engineering
modifications and appropriate valving changes. The heat engine and
the heat pump may likewise be combined into a single piece of
machinery by the exercise of ordinary engineering techniques.
In any of the embodiments or variations taught or suggested by the
instant disclosure various modifications in the apparatus utilized
may be made without deviating from the concept of the inventive
process. For example, the separate hot and cold water storage means
can be replaced by a single vessel wherein the hot and cold water
are kept separate by either the use of an insulating diaphragm or
merely by the inherent density differences of the stored water. It
must be noted however, that the same type of modification cannot be
utilized for the storage of hot and cold LVP energy storage
material since the difference between the temperatures would
subject the storage vessel to unacceptable physical strain and
subsequent deterioration.
The heat exchanger means encompasses any viable method of heat
transfer. The exchanger can be the classic shell-tube type heat
exchanger or greatly simplified so that heat is transferred from
steam to LVP or LVP to water by the direct contact of the two
materials. Those skilled in the art will be able to fashion many
such refinements of the instant process now that the basic
inventive process has been disclosed. Such refinements will not
detract nor will they add to the process of the instant invention,
such modification falling totally within the scope of the
invention.
As previously stated, it is also possible to combine the function
of two apparatus in a single mechanism. For example, the separate
heat pump means and turbine can be integrated into a single machine
capable of both functions (clearly however, at different times)
coupled into either separate electric motors and electric
generators or a combined motor/dynamo apparatus.
It must be understood that the representations contained in
Diagrams I and II are merely two of the typical ways in which the
concept of the instant disclosure can be utilized, any number of
modifications being possible and within the scope of ordinary
engineering procedures which will not detract or stray from the
scope of the instant disclosure.
* * * * *